Check out the Seventeen most powerful girls under 21, and pick up the March issue, on newsstands February 4th, for more on these power girls plus advice for living your dreams starting…now!

The Mogul: Selena Gomez

The Mogul: Selena Gomez

Selena is owning her place in the world. Her first solo album, Stars Dance, hit number one on the Billboard 200, and she’s packing the house at major venues on her tour. She’s such a fashion icon that she’s designing clothing lines for Kmart and Adidas. She heads a movie production company and is an investor in a cool app start-up. Between Facebook, Twitter, and Instagram, she has 77 million followers. And she’s using her star power to help children around the world succeed—and often, just survive—as UnIceF’s youngest-ever goodwill ambassador.

On feeling powerful: “This year is when I really started feeling powerful. I had always been the underdog secretly. I was on Disney when it was Miley [Cyrus], the Jonas Brothers, and Demi [Lovato]. I questioned the way I looked, acted, sang, and wrote. Then I turned 20, went through a really bad breakup, and realized I needed to have 'Come & Get It' be amazing. I wanted it all to be me. I'm glad it's taken me this long to get where I am because now I am ready for it."

The Cool Chick: Demi Lovato

The Cool Chick: Demi Lovato

Demi, 21, had a No. 1 song, judged The X Factor, and scored a best- selling book! But it’s her support of girls suffering from self-harm and addiction that puts Demi so high on our list.

When do you feel badass? “When I’m being influential to people who really need some guidance. I could keep my self-harm and addiction issues private, or I could use them to help other people. I chose the latter, and it’s been the best decision of my life.”